The most pleasing addition to the list of newspaper archives for 1901-1950 is the Spectator, the most influential conservative weekly of the period. The Spectator archive is free; near-complete from 1828 to 2008; contains both images and text -- and the OCR is high quality; tagged; and is easy to search or browse. However, there is no advanced search function (though you can use Boolean operators such as AND and NOT). While you can use the Trove-style filters to narrow a keyword search down to a decade of interest, you can't zoom into a year, let alone a month, week or day. There doesn't seem to be any easy way to save article images (the best way I've found is to zoom on the page and use the web browser to save as HTML; you get a lot of extra junk but among them are two usable images). And it's a shame that illustration captions and advertisements appear to have been excluded from the text search, though they are visible visually. Still, it's all still in beta, and did I mention that it's free?
Welsh Newspapers Online is expanding rapidly, having added the following titles:
Cambrian News and Merionethshire Standard
Cymro A'r Celt Llundain
Montgomeryshire Express and Radnor Times
North Wales Express
North Wales Weekly News
Rhyl Record and Advertiser
South Wales Daily Post
Weekly News and Visitors' Chronicle For Colwyn Bay
The coverage for most of these ends in 1910, as with most of WNO's titles; however, Cymro (published in Liverpool), Aberdare Leader, Cambrian News and Merionethshire Standard, Lials Llafur, and Merthyr Pioneer all cover at least the period 1914-1919. The war will be mentioned.
There's been some activity at the British Newspaper Archive too. The following titles have been added:
Luton News and Bedfordshire Advertiser
Some of these are only available for very short runs, however; for example, Inverness Courier from 1928 to 1930 (so no Nessie) and Luton News and Bedfordshire Advertiser for just 1950. However, some other titles have had substantial numbers of issues added: Edinburgh Evening News previously stopped in 1914 but now goes up to 1932; Gloucester Journal ranged from 1922 to 1949 but is now complete for the first half of the twentieth century; the Kent & Sussex Courier used to have only a few years of coverage but now goes right up to 1939. And so on.
Newspaper Archive, which prefers to be known as NewspaperARCHIVE.COM, continues on its frustrating way. It has added quite a few new titles since the last update:
Evening News and Evening Mail
The Monitor and New Age
North Middlesex Standard
North Middlesex Weekly
St James's Gazette
Some of these are interesting titles: M.A.P. (Mainly About People) was a gossip rag edited by T. P. O'Connor; The Monitor and New Age was a Catholic newspaper; Smith's Weekly (not to be confused with the later and more successful Sydney newspaper of the same name) featured short stories, humorous anecdotes, competitions and the like. So that's nice. But every silver lining has a cloud at NewspaperARCHIVE.COM. Here, the problem is that many of these new titles are listed under various different names with overlapping coverage. There's no apparent rhyme or reason, way to search across all the versions, or even links to them. For example, issues of the Evening News and Evening Mail can be found as London Evening News And Evening Mail (1901-1905), London Evening News (1901-1918), London Football Evening News (a single issue, 3 February 1904) and London Evening News And Post (again, a single issue, 15 August 1902). Name changes and mergers may be responsible for some of the confusion -- at some point and Evening Mail was dropped from the masthead -- but that doesn't explain why single issues would be filed under spurious names, or where Football Evening News came from. Similar errors dog the Middlesex Gazette, the North Middlesex Standard, and Smith's Weekly (which is listed under Smith's Weekly and St Smith's Weekly). This is utterly hopeless. Combined with the terrible search functionality, useless website and dubious customer relations I can't recommend NewspaperARCHIVE.COM. Unless you need something it has. (Unless it was the single year of the Hackney Mercury it had. Because it's no longer there.)
In other news, Irish Newspaper Archives has added the Longford Leader, complete for the entire period 1901 and 1950. The Scotsman's archive is now using the interface developed by BrightSolid for the BNA; however, it's not actually part of the BNA and is quite expensive for a single newspaper archive (it always was). The Tribune's archive is no longer working, I think because their tribunemagazine.co.uk domain has been taken over by cybersquatters. They have a tribunemagazine.org domain which is still working, but their new archive link doesn't work either. So I've taken it off for now.
Finally, I'll just mention Wikisource's 'Periodicals, General Interest' category and the serials list at the Online Books Page at the University of Pennsylvania. These collate links to some useful periodicals like Blackwood's Magazine from various sources like the Internet Archive; but due to the lack of any unified search across volumes they're not online archives in the same sense as the above. Only some are British, anyway.